Can our parents’ trauma be passed onto us? Well researchers seem to think it can, especially in extreme cases such as when discussing Holocaust victims and their children.

According to YNetNews, a research team at New York’s Mount Sinai hospital said this is the first demonstration of how psychological trauma endured by a person can have intergenerational effects on his offspring.

The research, which was published in the journal Biological Psychiatry, included 32 test subjects, Jewish men and women who were at concentration camps during the Holocaust, witnessed or experienced torture, or had to hide from the Nazis during World War II. In addition, they also analyzed the genes of 22 of their adult offspring and compared them to Jewish families who did not live in Europe during the Nazis’ rule.

They say people’s genes are modified by their environment through chemical tags that attach themselves to DNA, and researchers found these tags on the same part of the stress-hormone gene in both Holocaust survivors and their children. Researchers aren’t clear exactly how gene changes are inherited as chemical tags were previously assumed to be cleared before DNA is passed on to offspring during fertilization.

However, one thing they feel is certain is that the Children of Holocaust survivors were found to be three times more likely to develop post-traumatic stress disorder if they were exposed to a traumatic event than demographically similar Jewish people whose parents did not survive the Holocaust.

Researchers also found that children of Holocaust survivors had the same neuroendocrine or hormonal abnormalities that the Holocaust survivors and other people suffering from post-traumatic stress disorder had, leading them to the belief that post-traumatic stress disorder was associated with having a parent that had post-traumatic stress disorder.

Dr. Rachel Yehuda began looking into children of Holocaust survivors after setting up a clinic for survivors at Mount Sinai hospital. She started receiving phone calls from the survivors themselves and their children.

“What we began to see quite clearly was that offspring were reporting that they had been affected by the Holocaust in many different kinds of ways, but in a very coherent and cohesive pattern,” she said.

“They talked about feeling traumatized by witnessing the symptoms of their parents. And they talked about being traumatized by some of the expectations that the Holocaust had placed on them, such as that they are the reason their parents survived and therefore there was a whole set of things that they would now have to accomplish so that all the people that died— they could give their lives meaning. They had difficulty in any kind of a separation circumstance — divorce and those kinds of things. And they described essentially this problem in separating from their parents,” she added.